1. Field of the Invention
This invention relates generally to valves used to control flows of fluids, and more particularly to valves such as weir type diaphragm valves having moveable diaphragms to control flows.
2. Description of Related Art
Diaphragm valves have moveable diaphragms to control fluid flows, and are commonly used for processing high purity fluids used in the pharmaceutical, biotechnical, chemical, food, and semiconductor industries. Their prevalent use is mainly due to their exceptional ability to resist damage from fluids (e.g., reactive chemicals). The diaphragms are typically the only moving parts that come in contact with the fluids, and the diaphragms typically isolate other moving parts from the fluids.
A major disadvantage with diaphragm valves is that the diaphragms wear out and require periodic replacement. The diaphragm is typically a flexible material sandwiched between a bonnet and a body drawn together by tightening several fasteners. A problem arises in that the flexible diaphragm offers little resistance to forces exerted on the diaphragm as the fasteners are tightened. During assembly of a diaphragm valve, there is a tendency to over-tighten the fasteners in an effort to assure leak-proof junctions. Over-tightening of the fasteners causes over-compression of the diaphragm, which often results in rupture and early failure of the diaphragm.
Various solutions to this problem have been attempted in the prior art. Jacob, Jr., U.S. Pat. No. 6,047,953, for example, teaches a universal diaphragm made of elastomeric material having rigid solid compression restrainers incorporated within the perimeter of the diaphragm for preventing over-compression of the diaphragm during the assembly of a diaphragm valve. The compression restrainers can be designed to occupy several positions within the area of the diaphragm that is pressed between the bonnet and valve body of the diaphragm valve. The compression restrainers are bonded or vulcanized onto the surface of the elastomeric material making up the diaphragm.
Marcilese, U.S. Pat. No. 6,155,535, illustrates the use of similar stops incorporated into the bonnet and/or valve body.
Other patents of interest include Simmons, et al., U.S. Pat. No. 6,295,918, G. E. Nicholson, et al., U.S. Pat. No. 2,578,730, Parkinson, U.S. Pat. No. 4,421,295, R. Fortune, U.S. Pat. No. 2,891,763, Greenwood, U.S. Pat. No. 5,829,472, Gilchrist, et al., U.S. Pat. No. 5,386,849, W. O. Teeters, U.S. Pat. No. 2,575,775, Maula, et al., U.S. 2004/0262562, Zuniga, et al., U.S. Pat. No. 5,762,544, and Makoto, Japan 04310701 (diaphragm seal mechanism having a metal O-ring spacer).
It would be beneficial to have a valve with a moveable diaphragm clamped between a bonnet and a body and one or more structures that provide circumferential sealing between the bonnet and the body, and also prevent over-compression of the flexible diaphragm.